Market research in the UK shows that 60% of women prefer tampons with applicators. While in the US, Mother Jones reports that 88% of the tampons sold in 2015 were ones with a non bio-degradable plastic applicator, with sales of cardboard applicators significantly declining. Meanwhile, in Europe and other parts of the world where tampons are commonly used, so-called “digital” tampons (or applicator-less ones inserted with ones digits, or fingers) have outsold oneswith applicators for decades.

Blog posts abound from American expats discovering, to their horror, that most tampons sold outside the US are the kind they have to “shove inside” with their own finger. And, from the other point of view, a Reddit thread entitled “Women of the US, why are your tampons so huge?” displays many people learning, for the first time, that applicators even exist.

So why is there such a split in the kind of tampon women use?

The first tampon as we recognize it today—with a telescoping cardboard applicator—was invented and patented in 1929 by American Dr Earl Hass. He then sold it to Gertrude Tenderich, a business women who went on to start the company Tampax. By 1939, Tampax had set up a subsidiary in the UK, and the brand was largely responsible for introducing tampons (with applicators) to women in those countries until later competitors emerged. In the 1970s plastic applicators, introduced by Playtex, came onto the scene.

Meanwhile, in the 1940s in Germany, gynecologist Judith Esser-Mittag invented a digital tampon, called o.b, which gained popularity in western Europe. It wasn’t until the mid-seventies, that Johnson and Johnson (which then owned o.b.) introduced o.b. digital tampons to the US. By then, the applicator habit had been set.

As Sharra Vostral, professor of history at Purdue University and author of Under Wraps: A History of Menstrual Hygiene Technology, said, “It’s not that applicator-less tampons weren’t available in the States, it’s that Tampax became the predominate tampon company.”